Band saw blade

ABSTRACT

A bimetal band saw blade has a cutting edge with a plurality of cutting teeth defining repeating, variable pitch patterns and variable set patterns within pitch patterns. Each relatively heavy set tooth defines a first primary clearance angle, and each unset and relatively light set tooth defines a second primary clearance angle. Each first primary clearance angle is less than or equal to about 20°, each second primary clearance angle is less than or equal to about 25°, and each first primary clearance angle is within the range of about 4° to about 6° less than each second primary clearance angle. Each unset or light set tooth defines a greater gullet area than a respective heavy set tooth and/or a finer pitch than the respective heavy set tooth. Each tooth defines a positive rake angle within the range of about 3° to about 10°.

FIELD OF THE INVENTION

The present invention relates to saw blades, and more particularly, toband saw blades where the cutting teeth define variable clearance anglesand variable set patterns within variable pitch patterns.

BACKGROUND INFORMATION

In a typical manual “pull-down” band saw the force at which the band sawblade is fed into the work piece is not mechanically controlled, butrather is provided manually by the operator. As a result, the feed forceis limited and can vary depending on the physical strength and abilityof the operator. Such pull-down band saws can be used to cut metal workpieces including, for example, roll formed, structural shapes, such asmetal pipes, fence posts, and other metal work pieces defining unique orodd shaped profiles. The band saw blades used for such applications aretypically bi-metal with flexible, spring steel backings, and cuttingteeth with tool steel tips that are welded to the spring steel backings.Due to the relatively uncontrolled nature of the feed force in manualpull-down band saws, relatively high impact cutting forces can beimparted to the cutting teeth, particularly when cutting metal,structural work pieces. As a result, a primary failure mode of band sawblades used in such applications is tooth damage due to chipping at thetool steel tips and/or stripping of the teeth away from the band at thebi-metal weld region or interface.

One of the drawbacks of prior art band saw blades used in suchapplications is that the blades fail prematurely, particularly as aresult of the above-mentioned tooth chipping and/or stripping, andtherefore the blades do not provide as long a blade life as desired.Another drawback is that the band saw blades do not use themanually-supplied feed forces as efficiently as desired, and as aresult, the time required to cut through work pieces can be longer thandesired. Commercially available band saw blades utilize a variety ofmethodologies to provide more robust tooth forms and thereby increaseblade life. A first methodology utilizes neutral or relatively smallrake angles to maximize the included angle between the rake face andclearance surfaces of the teeth. A second methodology utilizes asomewhat reduced primary clearance angle in conjunction with a largersecondary clearance angle to maximize the included angle. A thirdmethodology utilizes a significantly reduced primary clearance angle inconjunction with a larger secondary clearance angle to maximize theincluded angle.

The present inventor has determined that these methodologies haveachieved varying and limited levels of effectiveness. The firstmethodology can cause the cutting to be less efficient than desiredwhile allowing for only relatively minimal gains in resisting toothstrippage. The second methodology, on the other hand, can be moreeffective at reducing tooth strippage, but can require longer cuttingtimes than desired. The third methodology also can be effective atreducing tooth stripping and chipping, but the tooth form definesrelatively small gullets that become more easily filled with chips. Thiscan reduce the rate at which the band saw is fed into the work piece,can cause the blade to stall and/or can lead to crooked cutting.

It is an object of the present invention to overcome one or more of theabove-described drawbacks and/or disadvantages of the prior art.

SUMMARY OF THE INVENTION

In accordance with one aspect, the present invention is directed to abimetal band saw blade with a cutting edge including a plurality ofcutting teeth defining repeating pitch patterns and set patterns withinpitch patterns. Each set pattern includes at least one unset orrelatively light set tooth, and at least one relatively heavy set tooth.A plurality of teeth within each pitch pattern define different pitchesthan a plurality of other teeth within the pitch pattern. Eachrelatively heavy set tooth defines a first primary clearance angle, andeach unset and relatively light set tooth defines a second primaryclearance angle. Each first primary clearance angle is less than orequal to about 20°, each second primary clearance angle is less than orequal to about 25°, and each first primary clearance angle is within therange of about 4° to about 6° less than each second primary clearanceangle. Each unset or light set tooth defines (a) a greater gullet areathan a respective heavy set tooth, and/or (b) a finer pitch than therespective heavy set tooth. Each tooth defines a positive rake anglewithin the range of about 3° to about 10°.

In some embodiments of the present invention, each tooth defines apositive rake angle that is greater than about 4°, is preferably greaterthan about 6°, and is more preferably greater than about 7°.

In some embodiments of the present invention, the band saw bladecomprises a blade body, and each set tooth defines a set equal to thedistance between an outer edge of the tooth and an adjacent side of anunset tooth or the blade body. Each light set tooth defines a set withinthe range of about 0.005 inch to about 0.007 inch, and preferably a setof about 0.006 inch, and each heavy set tooth defines a set within therange of about 0.008 inch to about 0.010 inch, and preferably a set ofabout 0.009 inch.

In some embodiments of the present invention, the band saw blade definesa cutting direction, and each pitch pattern comprises teeth thatdecrease in pitch in a direction opposite the cutting direction, from arelatively coarse pitch to a relatively fine pitch, and then increase inpitch from the relatively fine pitch to a relatively coarse pitch. Insome such embodiments, each pitch pattern consists of teeth thatprogressively decrease in pitch from one tooth to the next from arelatively coarse pitch to a relatively fine pitch, and thenprogressively increase in pitch from one tooth to the next from therelatively fine pitch to the relatively coarse pitch.

In some embodiments of the present invention, (i) each pitch patterndefines a variable pitch within the range of about 5 teeth per inch(“TPI”) to about 8 TPI, the first primary clearance angle is within therange of about 7° to about 11°, and is preferably about 9°, and thesecond primary clearance angle is within the range of about 13° to about17°, and is preferably about 15°; (ii) each pitch pattern defines avariable pitch within the range of about 6 TPI to about 10 TPI, thefirst primary clearance angle is within the range of about 10° to about14°, and is preferably about 12°, and the second primary clearance angleis within the range of about 16° to about 20°, and is preferably about18°; or (iii) each pitch pattern defines a variable pitch within therange of about 10 TPI to about 14 TPI, the first primary clearance angleis within the range of about 17° to about 21°, and is preferably about19°, and the second primary clearance angle is within the range of about22° to about 25°, and is preferably about 24°.

In some embodiments of the present invention, the band saw blade definesa cutting direction, and the gullet areas of the teeth in each pitchpattern decrease in a direction opposite the cutting direction from arelatively high gullet area at one end of the pitch pattern to arelatively low gullet area in a midsection of the pitch pattern, andthen increase from the relatively low gullet area to a relatively highgullet area at the other end of the pitch pattern. In some suchembodiments, the gullet areas of the teeth in each pitch patternprogressively decrease from one tooth to the next in a directionopposite the cutting direction from the relatively high gullet area atone end of the pitch pattern to the relatively low gullet area at themidsection of the pitch pattern, and then progressively increase inpitch from one tooth to the next from the relatively low gullet area tothe relatively high gullet area at the other end of the pitch pattern.

In some embodiments of the present invention, a plurality of teeth in amidsection of each pitch pattern define (i) the finest pitches of thepitch pattern, and/or (ii) the smallest gullet areas of the pitchpattern. In some such embodiments, each pitch pattern includes about tenteeth, and about three of the teeth at the midsection of the pitchpattern define (i) the finest pitches of the pitch pattern, and/or (ii)the smallest gullet areas of the pitch pattern. In some suchembodiments, each of the three teeth at the midsection are either unsetor light set teeth. In some embodiments of the present invention, thetooth in each pitch pattern defining (i) the smallest gullet area and/or(ii) the finest pitch, is an unset tooth located in the midsection ofthe pitch pattern.

In some embodiments of the present invention, at least one unset orlight set tooth defines a lesser gullet area and a finer pitch than arespective heavy set tooth. In some such embodiments, said at least oneunset or light set tooth is located in a midsection of the respectivepitch pattern. In some such embodiments, each of said at least one unsetor light set teeth defines a gullet area that is not less than about 60percent of the gullet area of any heavy set tooth. In some embodiments,each of said at least one unset or light set teeth defines a gullet areathat is within the range of about 50 percent to about 90 percent of thegullet area of any heavy set tooth.

In some embodiments of the present invention, each pitch pattern definesa total gullet area for all teeth within the respective pitch pattern,and the total gullet area of all heavy set teeth (i) is less than about45% of the total gullet area for all teeth in the respective pitchpattern, and (ii) is preferably less than about 40% of the total gulletarea for all teeth in the respective pitch pattern. Also in someembodiments the gullet area of each heavy set tooth is no more thanabout 12% of the total gullet area of all teeth in the respective pitchpattern, and preferably is no more than about 9% of the total gulletarea of all teeth within the respective pitch pattern.

In some embodiments, the band saw blade defines a cutting direction, andthe plurality of teeth define set patterns within each pitch pattern.Within each set pattern the teeth (i) increase in set in a directionopposite the cutting direction from an unset tooth to a light set toothto a heavy set tooth, and then (ii) decrease in set from a heavy settooth to a light set tooth to an unset tooth. In some such embodiments,within each set pattern the teeth (i) increase again from the unsettooth to a light set tooth to another heavy set tooth, and (ii) decreaseagain from a heavy set tooth to a light set tooth to another unsettooth. In some embodiments, each set pattern includes an unset or lightset tooth followed in a direction opposite the cutting direction by alight set tooth, a heavy set tooth, and then an unset or light settooth. In some such embodiments, the set pattern is repeated within thepitch pattern. In some such embodiments, the teeth of the repeating setpattern within the pitch pattern comprise an unset tooth followed in adirection opposite the cutting direction by a light set tooth set to afirst side of the blade body, a heavy set tooth set to a second side ofthe blade body opposite the first side, a heavy set tooth set to thefirst side, a light set tooth set to the second side, an unset tooth orlight set tooth, a light set tooth set to the first side, a heavy settooth set to the second side, a heavy set tooth set to the first side,and an unset or light set tooth.

Some embodiments of the present invention further comprise a blade bodyincluding a relatively flexible backing, such as a spring steel backing,a relatively hard portion, such as tool steel, defining the tips of thecutting teeth and welded to the backing, and a weld region therebetweenwhere the hard portion is welded to the flexible backing. Each toothincludes a cutting tip, a gullet extending between the tooth and anadjacent tooth, a protrusion located at the weld region between thegullet and the tip, and a rake face extending between the protrusion andthe cutting tip. The protrusion extends outwardly relative to contiguousportions of the rake face and gullet.

In accordance with another aspect, the present invention is directed toa bimetal band saw blade with a cutting edge including a plurality ofcutting teeth defining repeating pitch patterns and set patterns withinpitch patterns. At least one set pattern includes at least one unset orrelatively light set tooth, and at least one relatively heavy set tooth.A plurality of teeth within the pitch pattern define different pitchesthan a plurality of other teeth within the pitch pattern. Eachrelatively heavy set tooth defines a first primary clearance angle, andeach unset and relatively light set tooth defines a second primaryclearance angle. Each tooth defines a positive rake angle within therange of about 3° to about 10°. Each tooth includes (i) first means forpreventing tooth chipping and stripping; and (ii) second means forpreventing gullet overfill and associated blade stall and crookedcutting.

In some embodiments of the present invention, the first means is definedby each first primary clearance angle being within the range of about 4°to about 6° less than each second primary clearance angle, and eachsecond primary clearance angle being less than or equal to about 25°. Insome embodiments, the second means is defined by each unset or light settooth defining at least one of (a) a greater gullet area than arespective heavy set tooth, and (b) a finer pitch than the respectiveheavy set tooth.

One advantage of the present invention is that the first primaryclearance angles of the heavy set teeth are less than or equal to about20°. This feature provides relatively large included angles between theprimary clearance angles and rake faces of the heavy set teeth, andthereby provides a robust tooth form, including a relatively longbimetal weld interface, in the cutting teeth that encounter the mostsubstantial cutting forces. This, in turn, provides significantlyimproved resistance to the premature tooth stripping and chippingencountered in prior art band saw blades. Yet another advantage of thepresent invention is that the second primary clearance angles of theunset and light set teeth are less than or equal to about 25°. Althoughgreater than the first primary clearance angles, the second primaryclearance angles are nevertheless relatively shallow, providing forrelatively large included angles between the primary clearance anglesand rake faces of the unset and light set teeth, and thereby providing arobust tooth form, including a relatively long bimetal weld interface.This feature further contributes to providing significantly improvedresistance to the premature tooth stripping and chipping encountered inprior art band saw blades.

Another advantage of the present invention is that each unset and lightset tooth defines a greater gullet area than a respective heavy settooth and/or a finer pitch than the respective heavy set tooth. Theunset and light set teeth in each pitch pattern thus define a greatergullet capacity than the heavy set teeth in the pitch pattern, therebyproviding substantially improved resistance to gullet overfill, andsubstantially obviating the associated high manual feed forces, reducedfeed rates, blade stalling, and/or crooked cutting encountered in priorart band saw blades. Yet another advantage of this feature is that itcan allow for significantly faster cutting times in comparison to priorart band saw blades, particularly when cutting structural shapes, suchas structural, roll-formed metal work pieces.

A further advantage of embodiments of the band saw blades of the presentinvention is that each tooth defines a positive rake angle within therange of about 3° to about 10°, and which is preferably greater thanabout 4°, is more preferably greater than about 6°, and is even morepreferably greater than about 7°. The relatively large included anglesresulting from the shallow primary clearance angles allow for suchaggressive rake angles, without significantly impacting the robustnessof the tooth form, and thus without significantly impacting theresistance of the teeth to the stripping and chipping encountered inprior art band saw blades. On the other hand, the relatively aggressiverake angles contribute to achieving faster cutting times in comparisonto prior art band saw blades, particularly in manual pull-down bandsaws, such as when cutting structural, metal work pieces.

Accordingly, another advantage of the band saw blades of the presentinvention is that they balance toughness against cutting speed, wheretoughness is achieved with relatively shallow primary clearance angles,and cutting speed is achieved with increased overall gullet capacity ofthe unset and light set teeth as compared to the heavy set teeth, andwith aggressive rake angles for all teeth or substantially all teeth.

Another advantage of some embodiments of the present invention is thatthe light and heavy set teeth are set to a lesser degree than the lightand heavy set teeth, respectively, of prior art band saw blades. Morespecifically, each light set tooth defines a set within the range ofabout 0.005 inch to about 0.007 inch, and each heavy set tooth defines aset within the range of about 0.008 inch to about 0.010 inch. The lesserdegree of set imparts a relatively narrow kerf width to the work piecesin comparison to prior art band saw blades, which, in turn, contributesto more efficient cutting and significantly faster cutting times incomparison to prior art band saw blades, particularly when cuttingstructural shapes, such as structural, roll-formed metal work pieces.

Other objects and advantages of the present invention, and/or of thecurrently preferred embodiments thereof, will become more readilyapparent in view of the following detailed description of embodimentsand accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial, side elevational view of a band saw blade inaccordance with an embodiment of the present invention;

FIG. 2 is an enlarged, partial, side elevational view of a cutting toothof the band saw blade of FIG. 1;

FIG. 3 is a partial, front elevational view of several cutting teeth ofthe band saw blade of FIG. 1 showing an unset tooth, and left and rightset teeth on either side of the unset tooth;

FIG. 4 is a table illustrating dimensions and other features of band sawblades in accordance with three variable pitch embodiments of thepresent invention;

FIG. 5 is a graph illustrating the results of tests performed onembodiments of band saw blades of the present invention against severalprior art band saw blades to assess their resistance to tooth damage;

FIG. 6 is a graph illustrating the results of tests performed onembodiments of band saw blades of the present invention against severalprior art band saw blades to assess their performance or time of cut;and

FIG. 7 is a table summarizing the features of the tested band saw bladesof FIGS. 5 and 6.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In FIGS. 1 and 2, a band saw blade embodying the present invention isindicated generally by the reference numeral 10. The bade saw blade 10comprises a blade body 12 and a cutting edge defined by a plurality ofcutting teeth 14. In the illustrated embodiment, the band saw blade 10is a bimetal blade including a relatively flexible spring steel backing16 welded to a tool steel strip defining tool steel tips 18 on theteeth. As shown typically in broken lines in FIG. 2, a weld line 20 isformed between each tool steel cutting tip 18 and the spring steelbacking 16.

As also shown typically in FIG. 2, each tooth includes a cutting tip 22,a rake face 24 located on one side of the tip, a primary clearancesurface 26 located on an opposite side of the tip relative to the rakeface, a secondary clearance surface 28 located on an opposite side ofthe primary clearance surface relative to the tip, a gullet 30 locatedon an opposite side of the secondary clearance surface 28 relative tothe primary clearance surface 26, and a protrusion 32 overlying the weldline 20 and extending between the rake face 24 and gullet 30. Theprotrusion 32 may be the same as or substantially the same as any of theprotrusions disclosed in commonly assigned U.S. Pat. No. 6,601,495 whichis hereby expressly incorporated by reference in its entirety as part ofthe present disclosure.

In the illustrated embodiments, the cutting teeth 14 define variablepitch patterns, and variable set patterns within the pitch patterns. Thepitch of a tooth is the distance between the tip of that tooth and thetip of a successive tooth, or the distance between another point on thattooth and the same point on the successive tooth. In the illustratedembodiment, each pitch pattern includes 10 teeth, and each tooth definesa respective pitch P1 through P10. However, as may be recognized bythose of ordinary skill in the pertinent art based on the teachingsherein, this number is exemplary, and may be changed a desired orotherwise required.

As shown in FIG. 1, the blade 10 defines a cutting direction 34, and theplurality of teeth define repeating set patterns within each pitchpattern. Within the first set pattern, the teeth (i) increase in set ina direction opposite the cutting direction from an unset tooth to alight set tooth to a heavy set tooth; and (ii) then decrease in set froma heavy set tooth to a light set tooth to an unset tooth. Then, in thesecond or repeated set pattern, the teeth (i) increase in set from theunset tooth to a light set tooth to another heavy set tooth; and (ii)decrease in set from a heavy set tooth to a light set tooth to anotherunset tooth. More specifically, as shown in FIG. 1, the blade 10includes a first unset tooth (S) defining a pitch P1 followed in adirection opposite the cutting direction 34 by a second light set toothset to the right (R) defining a second pitch P2, a third heavy set toothset to the left (L(h)) defining a third pitch P3, a fourth heavy settooth set to the right (R(h)) defining a fourth pitch P4, a fifth lightset tooth set to the left (L) defining a fifth pitch P5, a sixth unsettooth (S) defining a pitch P6, a seventh light set tooth set to theright (R) defining a seventh pitch P7, an eighth heavy set tooth set tothe left (L(h)) defining an eighth pitch P8, a ninth heavy set tooth setto the right (R(h)) defining a ninth pitch P9, and a tenth light settooth set to the left (L) defining a tenth pitch P10.

As shown typically in FIG. 3, each set tooth defines a set equal to thedistance between an outer edge 36 of the tooth and an adjacent side 38of an unset tooth or the blade body 12. In the illustrated embodiments,each light set tooth ((L) and (R)) defines a set within the range ofabout 0.005 inch to about 0.007 inch, and preferably a set of about0.006 inch, and each heavy set tooth ((L(h)) and (R(h)) defines a setwithin the range of about 0.008 inch to about 0.010 inch, and preferablya set of about 0.009 inch.

As shown typically in FIG. 2, each tooth defines a primary clearanceangle 40 between the respective primary clearance surface 26 and a lineor reference plane extending parallel to the elongated axis of the bladebody or between the tips of successive unset teeth (S). Each heavy settooth ((L(h)) and (R(h)) defines a first primary clearance angle 40 ₁and each unset tooth (S) and light set tooth ((L) and (R)) defines asecond primary clearance angle 40 ₂. Each first primary clearance angle40 ₁ is less than or equal to about 20°, each second primary clearanceangle 40 ₂ is less than or equal to about 25°, and each first primaryclearance angle 40 ₁ is within the range of about 4° to about 6° lessthan each second primary clearance angle 40 ₂. Each tooth also defines asecondary clearance angle 41 between the respective secondary clearancesurface 28 and a line or reference plane extending parallel to theelongated axis of the blade body or between the tips of successive unsetteeth (S). In the illustrated embodiments, each secondary clearanceangle is within the range of 42° to about 52°, and is preferably withinthe range of about 44° to about 50°. In the illustrated embodiments,each secondary clearance angle 41 is about 46½°. As shown typically inFIG. 1, each gullet defines a depth “D” which is the axial distance fromthe tip 22 of the tooth to the base of the gullet.

As shown typically in FIG. 2, each tooth defines a respective gulletarea “GA” defined as the area below a line extending between the tips ofsuccessive teeth. Each unset (S) or light set tooth ((L) and (R))defines (i) a greater gullet area GA than a respective heavy set tooth((L(h)) and (R(h)), and/or (2) a finer pitch than the respective heavyset tooth. Each tooth 14 also defines a rake angle 42 which is the anglebetween the rake face 24 and an axis perpendicular to a reference plane,which may be defined by the plane extending between the tips ofsuccessive teeth having substantially the same height, such assuccessive unset teeth. A zero degree (0°) rake angle is aligned withthe perpendicular axis, a negative rake angle extends forwardly relativeto the perpendicular axis with respect to the cutting direction 34 ofthe blade, and a positive rake angle extends rearwardly relative to theperpendicular axis with respect to the cutting direction of the blade.Each tooth 14 defines a positive rake angle within the range of about 3°to about 10°. In the illustrated embodiments, each rake angle 42 ispreferably greater than about 4°, is more preferably greater than about6°, and is even more preferably greater than about 7°.

The currently preferred embodiments of the band saw blade definedifferent variable pitch patterns. In the illustrated embodiments, eachvariable pitch pattern consists of teeth that decrease in pitch in adirection opposite the cutting direction 34, from a relatively coarsepitch to a relatively fine pitch, and then increase in pitch from therelatively fine pitch to a relatively coarse pitch. One embodimentdefines a “5/8” variable pitch pattern, where the pitch varies withinthe range of about 5 teeth per inch (“TPI”) to about 8 TPI; anotherembodiment defines a “6/10” variable pitch pattern, where the pitchvaries within the range of about 6 TPI to about 10 TPI; and anotherembodiment defines a 10/14 pitch pattern, where the pitch varies withinthe range of about 10 TPI to about 14 TPI. In these embodiments, theprimary clearance angles 40 ₁ and 40 ₂ vary such that the coarser pitchpatterns define more shallow primary clearance angles than the finerpitch patterns. More specifically, (i) in the 5/8 variable pitch patternembodiment, the first primary clearance angle 40 ₁ is within the rangeof about 7° to about 11°, and is preferably about 9°, and the secondprimary clearance angle 40 ₂ is within the range of about 13° to about17°, and is preferably about 15°; (ii) in the 6/10 variable pitchpattern embodiment, the first primary clearance angle 40 ₁ is within therange of about 10° to about 14°, and is preferably about 12°, and thesecond primary clearance angle 40 ₂ is within the range of about 16° toabout 20°, and is preferably about 18°; and (iii) in the 10/14 variablepitch pattern embodiment, the first primary clearance angle 40 ₁ iswithin the range of about 17° to about 21°, and is preferably about 19°,and the second primary clearance angle 40 ₂ is within the range of about22° to about 25°, and is preferably about 24°.

In FIG. 4, the table illustrates the tooth type (i.e., (S), (R), (L),R(h) or L(h)), rake angle 42, primary clearance angle (40 ₁ or 40 ₂),pitch (P1 through P10), and gullet area (GA), for the ten teeth (1-10)in each of the 5/8, 6/10 and 10/14 variable pitch pattern embodiments.As can be seen, in each embodiment, the pitch progressively decreasesfrom one tooth to the next from a relatively coarse pitch to arelatively fine pitch, and then progressively increases in pitch fromone tooth to the next from the relatively fine pitch to the relativelycoarse pitch.

As shown in FIG. 4, in each of the 5/8, 6/10 and 10/14 variable pitchpattern embodiments, the gullet areas (GA) of the teeth decrease in adirection opposite the cutting direction 34 from a relatively highgullet area at one end of the respective pitch pattern to a relativelylow gullet area in a midsection of the pitch pattern, and then increasefrom the relatively low gullet area to a relatively high gullet area atthe other end of the pitch pattern. As also shown in FIG. 4, a pluralityof teeth in a midsection of each pitch pattern (teeth nos. 5, 6 and 7)define (i) the finest pitches of the pitch pattern, and/or (ii) thesmallest gullet areas of the pitch pattern. As can be seen, each of thethree teeth at the midsection are either unset (S) or light set teeth((L) or (R)). Also in each of these embodiments, the tooth defining (i)the smallest gullet area and (ii) the finest pitch, is an unset tooth(S) located in the midsection of the pitch pattern.

As also reflected in FIG. 4, each pitch pattern defines a total gulletarea for all teeth within the respective pitch pattern. Preferably, (i)the total gullet area of all heavy set teeth is less than about 45% ofthe total gullet area of all teeth in the respective pitch pattern, andis more preferably less than about 40% of the total gullet area of allteeth in the respective pitch pattern; and (ii) the gullet area of eachheavy set tooth is no more than about 12% of the total gullet area ofall teeth in the respective pitch pattern, and is more preferably nomore than about 9% of the total gullet area of all teeth in therespective pitch pattern. As shown typically in FIG. 4, one or more ofthe unset (S) or light set teeth ((L) or (R)) may define a lesser gulletarea GA and a finer pitch than a respective heavy set tooth. In theillustrated embodiments, such unset or light set tooth is located in amidsection of the respective pitch pattern. Preferably, each of such oneor more unset or light set teeth defines a gullet area that is not lessthan about 60 percent of the gullet area of any heavy set tooth, andpreferably is within the range of about 50 percent to about 90 percentof the gullet area of any heavy set tooth.

Two types of band saw blades embodying the present invention were testedagainst several types of prior art band saw blades to assess (i)resistance to tooth damage, and (ii) performance as measured by the timerequired to cut through test work pieces (“time of cut”). In sum, asshown graphically in FIGS. 5 and 6, the band saw blades embodying thepresent invention significantly outperformed the prior art band sawblades with respect to both resistance to tooth damage and performance.All band saw blades were tested on the same manual pull-down type bandsaw and were used to cut the same types of test work pieces. The bandsaw was a MEP Shark 260, all tested blades were about 9 feet-1 inch×1inch×0.035 inch. The guides on the band saw were spaced at about 10inches, and the blade tension was maintained at about 60 bar. Each bladewas tested for a maximum of 100 cuts with a 10 kg load hung from theband saw tensioning spindle. The test work pieces were “stuffed pipe”comprised of sections of #40 steel pipe with the following items weldedat one end within the interior of the pipe: (i) a 2 inch×½ inch bar of4140 alloy steel, (ii) a 11/4 inch×¼ inch bar of 304 stainless steel,(iii) 2 pieces of 1 inch×⅛ inch angle iron, and (iv) two pieces of #4rebar. Each work piece was about 24 inches long and could be used forabout eighty (80) test cuts. Due to the presence of stainless steel inthe work pieces, the band saw was run at the “slow” speed of about 154feet per minute. For each tested blade, the time for each cut throughthe work piece was measured. A maximum cut time of 150 seconds wasadopted for the test, but due to previously observed variability in cuttimes believed to be due to machine “warm-up” and changes in workpieces, no blade was deemed to fail due to time out (i.e., failure tocut through a work piece prior to expiration of the 150 second maximumcut time) unless the 150 second maximum cut time was exceeded on twoconsecutive cuts for the respective blade.

In testing resistance to tooth damage, a “damaged” tooth was chipped orstripped. As shown in FIG. 5, less than 0.2 percent of the teeth of thetested band saw blades of the invention were damaged, whereas in thetested prior art blades, 6.27 percent, 13.8 percent, and 2.4 percent, ofthe teeth were damaged, respectively. Accordingly, the band saw bladesof the invention demonstrated better than 10 times the tested resistanceto tooth damage than the best tested prior art band saw blades.

With respect to speed of cut, the cut times for the tested band sawblades embodying the present invention were significantly faster, andthus they outperformed the tested prior art band saw blades. As shown inFIG. 6, the band saw blades embodying the invention were blade types 4and 5. These blades had mean cut times of 71.03 and 65.37 seconds,respectively. The tested prior art blades (blade types 1, 2 and 3), onthe other hand, had mean cut times of 104.33, 83.83 and 112.57 seconds,respectively. Accordingly, the tested band saw blades embodying theinvention had significantly faster cut times than the tested prior artblades.

As can be seen from FIGS. 5 and 6, the tested band saw blades embodyingthe invention provide both significantly improved resistance to toothdamage and faster cut times than the tested prior art band saw blades.Further, no single tested prior art band saw blade provided a desiredcombination of both resistance to tooth damage and performance. Forexample, the best tested prior art band saw blade for resistance totooth damage was blade type 3, but this blade type provided the poorestcut times of all tested blade types (FIG. 6). Similarly, the best testedprior art band saw blade for time of cut was blade type 2, but thisblade type provided the poorest resistance to tooth damage of all testedblade types (FIG. 5).

FIG. 7 illustrates the features of each tested blade type. With respectto the nomenclature of FIG. 7, “Pitch (actual)” is the approximate pitchfollowed in parentheses by the measured or actual pitch; the “AverageD/P” is the average depth “D” divided by the pitch “P”; “P. Relief” isthe primary relief angle; “Min Band Width” is the minimum band width ininches; “T” is the number of teeth in the tooth pattern (“7T” is seventeeth in the tooth pattern, “8T” is eight teeth in the tooth pattern,and so on); and “Side Set” is the degree of set of the set teeth ininches. As can be seen, one key difference of the tested blades of theinvention (blade types 4 and 5) as compared to the tested prior artblades (blade types 1, 2 and 3) is that the blades of the inventionincluded primary clearance angles on the heavy set teeth (L(h) and R(h))of 9°, and primary clearance angles on the unset and light set teeth((S), (L) and (R)) of 15°. The present inventor determined that the moreshallow the primary clearance angle, the better is the resistance of theblade to tooth damage, but that such shallow primary clearance anglescould undesirably increase the time of cut. The present inventionovercomes this dilemma and provides significant advantages neithertaught nor suggested by the prior art by providing the most shallowprimary clearance angles on only the heavy set teeth. As a result, theteeth most susceptible to tooth damage are significantly more robust andresistant to such damage, while nevertheless maintaining sufficientoverall gullet volume (or gullet area) in the cutting teeth collectivelyto minimize or reduce the time of cut. These features, coupled with therelatively aggressive positive rake angles, allow the blades of thepresent invention to unexpectedly provide significant improvements withrespect to both resistance to tooth damage and time of cut over priorart band saw blades, particularly when used on manual pull-down bandsaws to cut metal, structural work pieces. As also shown in FIG. 7,blade type 5 of the invention had a lesser degree of set, and thus amore narrow kerf, than blade type 4 of the invention. As a result, bladetype 5 provided even faster performance (65.37 mean time of cut vs.71.03 mean time of cut). This relatively narrow kerf unexpectedly didnot result in the structural metal work pieces “springing back” andpinching the band saw blade.

As may be recognized by those of ordinary skill in the pertinent artbased on the teachings herein, numerous changes and modifications may bemade to the above-described and other embodiments of the presentinvention without departing from its scope as defined, for example, inthe appended claims. For example, the teeth of the band saw blades maydefine any of numerous different tooth forms, pitch patterns or setpatterns, or may be made of any of numerous different materials, thatare currently known, or that later become known. In addition, the bandsaw blades of the invention can be used on band saws other than manualpull-down band saws, and can be used to cut work pieces other thanstructural metal work pieces. Although the disclosed embodiments of theinvention are band saw blades, the features of the invention also couldbe employed in other types of saw blades, such as hole saws.Accordingly, this detailed description of embodiments is to be taken inan illustrative, as opposed to a limiting sense.

What is claimed is:
 1. A band saw blade comprising a bimetal blade bodyand a cutting edge defined by a plurality of cutting teeth withrepeating pitch patterns and set patterns within pitch patterns,wherein: (i) at least one set pattern includes at least one unset orrelatively light set tooth, and at least one relatively heavy set tooth;(ii) a plurality of teeth within the pitch pattern define differentpitches than a plurality of other teeth within the pitch pattern; (iii)each relatively heavy set tooth defines a first primary clearance angle,each unset and relatively light set tooth defines a second primaryclearance angle, each first primary clearance angle is less than orequal to about 20°, each second primary clearance angle is less than orequal to about 25°, and each first primary clearance angle is within therange of about 4° to about 6° less than each second primary clearanceangle; (iv) each unset or light set tooth defines at least one of (a) agreater gullet area than a respective heavy set tooth, and (b) a finerpitch than the respective heavy set tooth; and (v) each tooth defines apositive rake angle within the range of about 3° to about 10°.
 2. A bandsaw blade as defined in claim 1, wherein each tooth defines a positiverake angle that is greater than at least one of (i) about 4°, (ii) about6°, and (iii) about 7°.
 3. A band saw blade as defined in claim 1,further comprising a blade body, wherein each set tooth defines a setequal to the distance between an outer edge of the tooth and an adjacentside of an unset tooth or a blade body, each light set tooth defines aset within the range of about 0.005 inch to about 0.007 inch, and eachheavy set tooth defines a set within the range of about 0.008 inch toabout 0.010 inch.
 4. A band saw blade as defined in claim 1, wherein theband saw blade defines a cutting direction, and each pitch patterncomprises teeth that decrease in pitch in a direction opposition thecutting direction from a relatively coarse to a relatively fine pitch,and then increase in pitch from the relatively fine pitch to arelatively coarse pitch.
 5. A band saw blade as defined in claim 4,wherein the each pitch pattern comprises teeth that progressivelydecrease in pitch from one tooth to the next from a relatively coarsepitch to a relatively fine pitch, and then progressively increase inpitch from one tooth to the next from the relatively fine pitch to arelatively coarse pitch.
 6. A band saw blade as defined in claim 5,wherein the band saw blade defines a cutting direction, and theplurality of teeth define a first set pattern within the pitch pattern,and within the first set pattern the teeth (i) increase in set in adirection opposite the cutting direction from an unset or light settooth to a heavy set tooth, and (ii) decrease in set from a heavy settooth to a light set or unset tooth.
 7. A band saw blade as defined inclaim 6, wherein the plurality of teeth define a second set pattern thatfollows the first set pattern in a direction opposition the cuttingdirection of the blade within each pitch pattern, and within the secondset pattern the teeth (i) increase in set in a direction opposite thecutting direction from an unset or light set tooth to a heavy set tooth,and (ii) decrease in set from a heavy set tooth to a light set or unsettooth.
 8. A band saw blade as defined in claim 7, wherein the teeth ineach of the first and second set patterns include an unset toothfollowed in a direction opposite the cutting direction by a light settooth, a heavy set tooth, another heavy set tooth, and then a light settooth.
 9. A band saw blade as defined in claim 7, wherein the bladeincludes a blade body, and each set pattern includes an unset toothfollowed in a direction opposite the cutting direction by a light settooth set to a first side of the blade body, a heavy set tooth set to asecond side of the blade body opposite the first side, a heavy set toothset to the first side, a light set tooth set to the second side, anunset tooth or light set tooth, a light set tooth set to the first side,a heavy set tooth set to the second side, a heavy set tooth set to thefirst side, and an unset or light set tooth.
 10. A band saw blade asdefined in claim 1, wherein (i) each pitch pattern defines a variablepitch within the range of about 5 teeth per inch (“TPI”) to about 8 TPI,the first primary clearance angle is within the range of about 7° toabout 11°, and the second primary clearance angle is within the range ofabout 13° to about 17°; (ii) each pitch pattern defines a variable pitchwithin the range of about 6 TPI to about 10 TPI, the first primaryclearance angle is within the range of about 10° to about 14°, and thesecond primary clearance angle is within the range of about 16° to about20°; or (iii) each pitch pattern defines a variable pitch within therange of about 10 TPI to about 14 TPI, the first primary clearance angleis within the range of about 17° to about 21°, and the second primaryclearance angle is within the range of about 22° to about 25°.
 11. Aband saw blade as defined in claim 10, wherein (i) each pitch patterndefines a variable pitch within the range of about 5 TPI to about 8 TPI,the first primary clearance angle is about 9°, and the second primaryclearance angle is about 15°; (ii) each pitch pattern defines a variablepitch within the range of about 6 TPI to about 10 TPI, the first primaryclearance angle is about 12°, and the second primary clearance angle isabout 18°; or (iii) each pitch pattern defines a variable pitch withinthe range of about 10 TPI to about 14 TPI, the first primary clearanceangle is about 19°, and the second primary clearance angle is about 24°.12. A band saw blade as defined in claim 1, wherein each pitch patterndefines a total gullet area for all teeth within the respective pitchpattern, and the total gullet area of the heavy set teeth is at leastone of (i) less than about 45% of the total gullet area of all teeth inthe respective pitch pattern, and (ii) less than about 40% of the totalgullet area of all teeth in the respective pitch pattern.
 13. A band sawblade as defined in claim 1, wherein the band saw blade defines acutting direction, and the gullet areas of the teeth in each pitchpattern decrease in a direction opposite the cutting direction from arelatively high gullet area at one end of the pitch pattern to arelatively low gullet area in a mid-portion of the pitch pattern, andthen increase from the relatively low gullet area to a relatively highgullet area at another end of the pitch pattern.
 14. A band saw blade asdefined in claim 13, wherein the gullet areas of the teeth in each pitchpattern progressively decrease from one tooth to the next in a directionopposite the cutting direction from a relatively high gullet area at oneend of the pitch pattern to a relatively low gullet area, and thenprogressively increase from one tooth to the next from the relativelylow gullet area to a relatively high gullet area at the other end of thepitch pattern
 15. A band saw blade as defined in claim 1, wherein aplurality of teeth in a midsection of each pitch pattern define at leastone of (i) the finest pitches of the pitch pattern, and (ii) thesmallest gullet areas of the pitch pattern.
 16. A band saw blade asdefined in claim 15, wherein each pitch pattern includes about tenteeth, and includes about three teeth at the midsection of the pitchpattern defining at least one of (i) the finest pitches of the pitchpattern, and (ii) the smallest gullet areas of the pitch pattern.
 17. Aband saw blade as defined in claim 16, wherein each of said three teethare either unset or light set teeth.
 18. A band saw blade as defined inclaim 1, wherein the tooth of each pitch pattern defining at least oneof (i) the smallest gullet area, and (ii) the finest pitch, is an unsettooth.
 19. A band saw blade as defined in claim 1, wherein at least oneunset or light set tooth defines a lesser gullet area and a finer pitchthan a respective heavy set tooth.
 20. A band saw blade as defined inclaim 19, wherein said at least one unset or light set tooth is locatedin a midsection of the respective pitch pattern.
 21. A band saw blade asdefined in claim 19, wherein said at least one unset or light set toothdefines a gullet area that is not less than about 60 percent of thegullet area of the respective heavy set tooth.
 22. A band saw blade asdefined in claim 21, wherein said at least one unset or light set toothdefines a gullet area that is within the range of about 50 percent toabout 90 percent of the gullet area of the respective heavy set tooth.23. A band saw blade as defined in claim 1, further comprising a bladebody including a relatively flexible backing, a relatively hard portiondefining the tips of the cutting teeth welded to the backing, and a weldregion therebetween welding the hard portion to the backing, and whereineach tooth includes a cutting tip, a gullet extending between the toothand an adjacent tooth, a protrusion located at the weld region betweenthe gullet and the tip, and a rake face extending between the protrusionand the cutting tip, wherein the protrusion extends outwardly relativeto contiguous portions of the rake face and gullet.
 24. A band saw bladecomprising a bimetal blade body and a cutting edge defined by aplurality of cutting teeth with repeating pitch patterns and setpatterns within pitch patterns, wherein: (i) at least one set patternincludes at least one unset or relatively light set tooth, and at leastone relatively heavy set tooth; (ii) a plurality of teeth within thepitch pattern define different pitches than a plurality of other teethwithin the pitch pattern; (iii) each relatively heavy set tooth definesa first primary clearance angle, each unset and relatively light settooth defines a second primary clearance angle; (iv) each tooth definesa positive rake angle within the range of about 3° to about 10°; (v)each tooth includes first means for preventing tooth chipping andstripping; and (vi) each tooth includes second means for preventinggullet overfill and associated blade stall and crooked cutting.
 25. Aband saw blade as defined in claim 24, wherein the first means isdefined by each first primary clearance angle being within the range ofabout 4° to about 6° less than each second primary clearance angle, andeach second primary clearance angle being less than or equal to about25°; and the second means is defined by each unset or light set toothdefining at least one of (a) a greater gullet area than a respectiveheavy set tooth, and (b) a finer pitch than the respective heavy settooth.